Shower Energy Research Articles

Lateral Distribution Functions of Signals in Surface Scintillation Detectors of the Yakutsk Array, New Energy Estimates of Extensive Air Showers and the Energy Spectrum of the Primary Cosmic Radiation at Energies ∼1017–1019 eV

Fluctuations of lateral distributions of signals in the surface scintillation detectors of the Yakutsk array are found to be large. New estimates of the inclined shower energy had been suggested. In view of these estimates the Yakutsk energy spectrum becomes quite comparable with the spectra observed at the Pierre Auger Observatory and the Telescope Array. The shower energy calculated using the data of only one detector may be overestimated if fluctuations are neglected.

Data-driven estimation of the invisible energy of cosmic ray showers with the Pierre Auger Observatory

The determination of the primary energy of extensive air showers using the fluorescence detection technique requires an estimation of the energy carried away by particles that do not deposit all their energy in the atmosphere. This estimation is typically made using Monte Carlo simulations and thus depends on the assumed primary particle mass and on model predictions for neutrino and muon production. In this work we present a new method to obtain the invisible energy from events detected by the Pierre Auger Observatory. The method uses measurements of the muon number at ground level, and it allows us to significantly reduce the systematic uncertainties related to the mass composition and the high energy hadronic interaction models, and consequently to improve the estimation of the energy scale of the Pierre Auger Observatory.3 MoreReceived 24 January 2019DOI:https://doi.org/10.1103/PhysRevD.100.082003© 2019 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCosmic ray & astroparticle detectorsTechniquesCosmic rays & astroparticlesGravitation, Cosmology & AstrophysicsParticles & Fields

CALPRO—a unconventional calorimetry project

We propose a unconventional calorimetry approach. The method is based on idea used for the first time in the energy determination of extensive air showers (EAS) at very high energy (> 100 TeV). It has some peculiar characteristics which can be summarized in the following two points: a) measurement of the shower energy by means of a single sampling; b) measurement of the lateral density distribution of charged particles around the shower axis. We studied the validation of this measurement technique to lower energies (100 GeV–10 TeV) by MC calculation.

Measurement of the Crab Nebula Spectrum Past 100 TeV with HAWC

Abstract We present TeV gamma-ray observations of the Crab Nebula, the standard reference source in ground-based gamma-ray astronomy, using data from the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory. In this analysis we use two independent energy estimation methods that utilize extensive air shower variables such as the core position, shower angle, and shower lateral energy distribution. In contrast, the previously published HAWC energy spectrum roughly estimated the shower energy with only the number of photomultipliers triggered. This new methodology yields a much-improved energy resolution over the previous analysis and extends HAWC’s ability to accurately measure gamma-ray energies well beyond 100 TeV. The energy spectrum of the Crab Nebula is well fit to a log-parabola shape with emission up to at least 100 TeV. For the first estimator, a ground parameter that utilizes fits to the lateral distribution function to measure the charge density 40 m from the shower axis, the best-fit values are (TeV cm2 s)−1, , and . For the second estimator, a neural network that uses the charge distribution in annuli around the core and other variables, these values are (TeV cm2 s)−1, , and β = 0.06 ± 0.01 ± 0.02. The first set of uncertainties is statistical; the second set is systematic. Both methods yield compatible results. These measurements are the highest-energy observation of a gamma-ray source to date.

Fluctuations of the Maximum Depth of EASes with Energies Greater than 1017 eV, According to Measurements of Radio Emission at Frequencies of 30–35 MHz

Results on the longitudinal development of extensive air showers (EAS) of ultrahigh energies are obtained from observations of radio emission at the Yakutsk array for the periods from 1986 to 1989 and from 2009 to 2014. The maximum depth of individual showers is determined and a statistical analysis of Xmax is performed to estimate the fluctuations in the development of EAS σ(Xmax) in the energy region of 1017–1018 eV. It is shown that σ(Xmax) is 50–60 g cm2 in the energy range of 1017–1018 eV, which does not contradict the mixed composition of cosmic rays (protons and helium nuclei). Data on the dependence of Xmax on energy also indicate this.

Precise Reconstruction of a Shower Maximum in the Tunka Radio Extension Experiment

Tunka-Rex is an antenna array located in the Tunka Valley that measures the radio emissions of cosmic ray air showers with energies of up to 100 PeV. In this work, a precise technique for reconstructing a shower maximum from Tunka-Rex data is presented. A model is developed for calculating detector efficiency that considers different parameters: primary particle energy and mass ranges, shower geometry, and detector configuration. The systematic error introduced by the atmosphere in reconstructing a shower’s maximum depth is estimated, and the distribution of the mean shower maximum versus energy is determined.

Mass composition of cosmic rays above 0.1 EeV by the Yakutsk array data

The paper presents the results of the longitudinal development of extensive air showers (Xmax) of ultra-high energies and mass composition of cosmic rays. The measurements of Xmax are based on data from observations of the Cherenkov radiation at the Yakutsk array for the period 1974–2014. The cascade curves of individual showers and the depth of maximum Xmax were reconstructed over the energy range 1016–5.7 · 1019 eV. It is shown that the displacement rate of the parameter dXmax/dE in the atmosphere is nonlinear and depends on the energy. Such a feature indicates a change in mass composition, which is confirmed by fluctuations of Xmax in this energy region. The composition of cosmic rays was determined by interpolation using the QGSJetII-04 model.

Unusual Time Structure of Extensive Air Showers at Energies Exceeding 1017 eV

Extensive air showers characterized by a multicomponent time structure were detected at the experimental Horizon-T array deployed at the Tien Shan High-Altitude Science Station of Lebedev Physical Institute, Russian Academy of Sciences, at an altitude of 3346 meters above sea level. Such a structure manifested itself in showers of energy above 1017 eV and suggests that, in contrast to the standard mechanism of the development of a nuclear-electromagnetic cascade, shower particles reach the observation level as components of several shower disks.

Leptoquark solution for both the flavor and ANITA anomalies

The ANITA experiment has seen anomalous Earth emergent showers of EeV energies which cannot be explained with Standard Model interactions. In addition, tests of lepton flavor universality in $ R(D^{(\ast)})$ and $R(K^{(\ast)})$ have shown significant deviations from theoretical predictions. It is known that, among single leptoquark solutions, only the chiral vector leptoquark $U_1 \sim (\mathbf{3}, \mathbf{1} , 2/3)$ can simultaneously address the discrepancies. In this paper, we show that the leptoquark motivated by flavor anomalies coupled to a sterile neutrino can also explain the ANITA Anomalous Events. We consider two scenarios, (a) the sterile neutrino, produced via resonant leptoquark mediated neutrino-nucleon interactions, propagates through the Earth without significant attenuation and decays near the surface to a $\tau$ lepton; and (b) a cosmogenic sterile neutrino interacts with the matter near the surface of Earth and generates a $\tau$ lepton. These two scenarios give significantly large survival probabilities even when regeneration effects are not taken into account. In the second scenario, the distribution of emergent tau energy peaks in the same energy range as seen by ANITA.

The CALorimetric Electron Telescope (CALET) on the International Space Station

The CALorimetric Electron Telescope (CALET) space experiment, developed by Japan in collaboration with Italy and the United States, is a high-energy astroparticle physics mission installed on the International Space Station (ISS). The primary goals of the CALET mission include investigating on the possible presence of nearby sources of high-energy electrons, studying the details of galactic particle propagation and searching for dark matter signatures. During a two-year mission, extendable to five years, CALET can measure the flux of cosmic-ray electrons (including positrons) to 20 TeV, gamma-rays to 10 TeV and nuclei with Z = 1 to 40 up to 1,000 TeV. The instrument consists of two layers of segmented plastic scintillators for cosmic-ray charge identification (CHD), a 3 radiation length thick tungsten-scintillating fiber imaging calorimeter (IMC) and a 27 radiation length thick lead-tungstate calorimeter (TASC). CALET has sufficient depth, imaging capabilities and excellent energy resolution to allow for a clear separation between hadrons and electrons and between charged particles and gamma rays. The instrument was launched on August 19, 2015 to the ISS with the H-II Transfer Vehicle 5 (HTV-5) and installed on the Japanese Experiment Module-Exposed Facility (JEM-EF) on August 25. Since the start of operations in mid-October, 2015, a continuous observation has been going on mainly by triggering high energy (>10 GeV) showers without any major interruption. The number of triggered events above 10 GeV is nearly 20 million per month. By using the data obtained during the first two years, we give a summary of CALET observations: (1) Electron + Positron energy spectrum, (2) Proton and Nuclei spectrum, (3) Gamma-ray observation, with results of the performance study on orbit. We also present the results of observations of the electromagnetic counterparts to LIGO-VIRGO gravitational wave events and high-energy counterparts to GRB events measured with the CALET Gamma-ray Burst Monitor (CGBM).

Determination of cosmic-ray primary mass on an event-by-event basis using radio detection

We present a new methodology to discriminate between light and heavy ultra-high energy cosmic-ray primaries on an event-by-event basis using information from the radio detection of extensive air showers at MHz frequencies. Similarly to other methods to determine primary cosmic ray composition, the one presented here is based on comparisons between detected radio signals and Monte Carlo simulations for multiple primary cosmic ray compositions. Unlike other methods that first reconstruct the depth of maximum shower development Xmax to relate it to the nature of the primaries, we instead infer the cosmic-ray composition directly. The method is most effective in the case of inclined showers that arrive at large zenith angles with respect to the vertical to the ground, where methods based on the determination of Xmax lose accuracy. We show that a discrimination efficiency between 65% and 80% can be reached for zenith angles θ ≳ 60∘, even when typical uncertainties in radio detection are taken into account, including shower energy uncertainty. Our methodology could in principle be applied in large and sparse radio arrays, designed with the large radio footprint of inclined showers in mind, to significantly increase the statistics of ultra-high energy cosmic-ray composition studies.

Determination of the invisible energy of extensive air showers from the data collected at Pierre Auger Observatory

In order to get the primary energy of cosmic rays from their extensive air showers using the fluorescence detection technique, the invisible energy should be added to the measured calorimetric energy. The invisible energy is the energy carried away by particles that do not deposit all their energy in the atmosphere. It has traditionally been calculated using Monte Carlo simulations that are dependent on the assumed primary particle mass and on model predictions for neutrino and muon production. In this work the invisible energy is obtained directly from events detected by the Pierre Auger Observatory. The method applied is based on the correlation of the measurements of the muon number at the ground with the invisible energy of the showers. By using it, the systematic uncertainties related to the unknown mass composition and to the high energy hadronic interaction models are significantly reduced, improving in this way the estimation of the energy scale of the Observatory.

Report on Tests and Measurements of Hadronic Interaction Properties with Air Showers

We present a summary of recent tests and measurements of hadronic interaction properties with air showers. This report has a special focus on muon density measurements. Several experiments reported deviations between simulated and recorded muon densities in extensive air showers, while others reported no discrepancies. We combine data from eight leading air shower experiments to cover shower energies from PeV to tens of EeV. Data are combined using the z-scale, a unified reference scale based on simulated air showers. Energy-scales of experiments are cross-calibrated. Above 10 PeV, we find a muon deficit in simulated air showers for each of the six considered hadronic interaction models. The deficit is increasing with shower energy. For the models EPOS-LHC and QGSJet-II.04, the slope is found significant at 8 sigma.

Systematic uncertainty of first-principle calculations of the radiation energy emitted by extensive air showers

The energy of extensive air showers can be determined from the energy radiated in the form of radio signals. The so-called radiation energy can be predicted with modern simulation codes using first-principle calculations without the need of free parameters. Here, we verify the consistency of radiation energy calculations by comparing a large set of Monte Carlo simulations made with the two codes CoREAS and ZHAireS. For the frequency band of 30 — 80 MHz, typically used by many current radio detectors, we observe a difference in the radiation energy prediction of 5.2%. This corresponds to a radio emission modelling uncertainty of 2.6% for thedetermination of the absolute cosmic-ray energy scale. Hence, radio detection offers the opportunity for a precise, accurate and independent measurement of the absolute energy of cosmic rays.

Characteristics of air showers with energy more than 1017 eV reconstructed by the Yakutsk array radio emission measurements

The paper presents results on the longitudinal development of air showers of ultra-high energies obtained from radio emission measurements at the Yakutsk array. The energy, the depth of maximum development of individual showers are determined and a statistical analysis of Xmax in order to estimate the fluctuation of air shower development σ(Xmax) in the energy region 1017-1018 eV is performed. It is shown that σ(Xmax) in the energy region 1017-1018 eV is equal to 50-60 g·cm-2, which doesn’t contradict with a mixed composition of cosmic rays - protons and helium nuclei. This is also indicated by data of the Xmax value dependence on energy.

Simulation of the fluorescence signal detected by a space telescope for extreme energy cosmic ray observations

The experimental technique of fluorescence light measurement is used for indirect observations of cosmic ray particles at very high energies. Extensive Air Showers (EAS) initiated by Extreme Energy Cosmic Rays (EECRs), up to 100 EeV and entering the Earth’s atmosphere, are simulated with the CORSIKA package. The influence of different simulation parameters on the EAS characteristics is studied, especially on the longitudinal distribution of charged particles, depth of shower maximum and energy released to the air. By taking the atmospheric scattering of light into account, the number of fluorescence photons, with wavelengths between 300-430 nm, and their arrival time distribution to an ideal space telescope are calculated.

A template-based γ-ray reconstruction method for air shower arrays

We introduce a new Monte Carlo template-based reconstruction method for air shower arrays, with a focus on shower core and energy reconstruction of γ-ray induced air showers. The algorithm fits an observed lateral amplitude distribution of an extensive air shower against an expected probability distribution using a likelihood approach. A full Monte Carlo air shower simulation in combination with the detector simulation is used to generate the expected probability distributions. The goodness of fit can be used to discriminate between γ-ray and hadron induced air showers. As an example, we apply this method to the High Altitude Water Cherenkov γ-ray Observatory and its recently installed high-energy upgrade. The performance of this method and the applicability to air shower arrays with mixed detector types makes it a promising reconstruction approach for current and future instruments.

Analysis of atmospheric attenuation using the Telescope Array central laser data

Located in the western desert of the state of Utah, the Telescope Array (TA) experiment measures the properties of ultra high energy cosmic ray (UHECR) induced extensive air showers. TA employs a hybrid detector comprised of a large surface array of scintillator detectors overlooked by three fluorescence telescopes stations. The TA Low Energy extension (TALE) detector has operated as a monocular Cherenkov/fluorescence detector for nearly five years, and has recently been complemented by a closely spaced surface array to operate in hybrid mode. The TAx4 upgrade is underway and aims to, as the name suggests, quadruple the size of the surface array to improve statistics at the highest energies (post-GZK events). The analysis of the TA fluorescence detectors (FD) data requires knowledge of the degree of the atmospheric attenuation of UV light produced by shower particles. This attenuation depends partially on the amount of aerosols present in the atmosphere at the time of shower observation. Being highly variable, real time measurement of the aerosols light attenuation is accomplished through the use of a central laser facility (CLF) located at the center of the surface array, and in the field of view of the three FDs, as well as, the TALE FD. In this proceeding we will describe the experiment, and the CLF data and analysis, and give results on measured aerosols attenuation, yearly averaged. FD measurements of shower energy and Xmax, involve corrections for atmospheric attenuation due to the presence of aerosols. We discuss the errors introduced into the shower parameters reconstruction due to uncertainty about aerosols attenuation.

Studies for high energy air shower identification using RF measurements with the ASTRONEU array

The Hellenic Open University (HOU) Cosmic Ray Telescope (ASTRONEU) consists of 9 large scintillator detectors and 3 RF antennas arranged in three autonomous stations operating at the Hellenic Open University campus in the city of Patras. High energy showers that are detected simultaneously by two distant stations and in coincidence with the RF antennas are used to study the RF signature of cosmic events. In previous studies we have shown that the timing of the RF signals as well as the measured electric field at the antennas position are in very good agreement with the simulation predictions. In this work we concentrate on the transfer functions of the antennas which are strongly frequency and angular dependent. We show that the RF spectra (at frequencies 30-80 MHz) of the detected showers are exhibiting features of the antenna response as predicted by detailed Monte Carlo simulation suggesting that a single antenna RF spectrum gives access to the cosmic ray arrival direction.

Hybrid Detection of High Energy Showers in Urban Environments

The Astroneu array comprises 9 large charged particle detectors and 3 RF antennas arranged in three autonomous stations operating at the University Campus of the Hellenic Open University in the city of Patras. Each station of the array detects extensive air showers with primary energy threshold of about 10 TeV, while double station coincidence events select showers with energies higher than 10 3 TeV. In such an environment, the radio detection of air showers is challenging. The RF signals besides being extremely weak they also suffer from strong human made electromagnetic noise. In this work, we present the analysis of double station coincidence events and we study the correlation of the RF data with the particle detectors data. We use the experimental information from the particle detectors and the antennas to select very high energy showers and we compare the timing of the RF signals with the timing of the particle detector signals as well as the strength of the RF signals with the simulation predictions.